双向链表结构体声明
typedef struct DNode
{int data;struct DNode *prior;struct DNode *next;
} DNode, *DLinkList;
（1)初始化
void InitDulList(DLinkList plist)
{assert(plist != NULL);if(plist == NULL)return;plist->prior=plist->next=NULL;
}
（2）静态函数：申请节点内存
static DLinkList ApplyNode(DLinkList next, DLinkList prior, int val)
{DLinkList s=(DNode *) malloc (sizeof (DNode));assert(s != NULL);if(s == NULL)return NULL;s->data=val;s->next=next;s->prior=prior;return s;
}
（3）求链表长度
int Listlength(DLinkList plist)
{assert(plist != NULL);if(plist == NULL)return -1;int count = 0;DLinkList p=plist->next; //p指向头的下一个，即第一个有效结点while(p != NULL){count++;p=p->next;}return count;
}
（4）得到某个结点，函数返回该结点
DLinkList GetNode(DLinkList plist, int pos)
{assert(plist != NULL);if(plist == NULL)return NULL;if(pos < 0)return NULL;DLinkList p=plist;while(pos && p != NULL){p=p->next;pos--;}return p;
}
（5）插入
void Insert(DLinkList plist, int pos, int val)
{assert(plist != NULL);if(plist == NULL)return;DLinkList p = GetNode(plist, pos); //要插入其后的结点的位置DLinkList s = ApplyNode(p->next, p, val); //要插入的结点if(p->next != NULL) //尾插单独考虑{p->next->prior=s; }p->next = s;
}
（6）头插
void InsertHead(DLinkList plist, int val)
{assert(plist != NULL);if(plist == NULL)return; DLinkList s=ApplyNode(plist->next, plist, val);if(plist->next != NULL) //若此时链表内没有有效数据，为空链{plist->next->prior = s;}plist->next = s;
}
（7）尾插
void InsertTail(DLinkList plist, int val)
{assert(plist != NULL);if(plist == NULL)return;Insert(plist, Listlength(plist), val);
}
（8）删除
void Delete(DLinkList plist, int pos)
{assert(plist != NULL);if(plist == NULL)return;if(pos<0 || pos>Listlength(plist)){return;}DLinkList p=GetNode(plist,pos); //要删除的结点if(p == NULL || p == plist) return;p->prior->next=p->next; if(p->next != NULL) //尾删无next{p->next->prior=p->prior;}free(p);
}
（9）头删
void DeleteHead(DLinkList plist)
{assert(plist != NULL);if(plist == NULL)return;Delete(plist,1);
}
（10）尾删
void DeleteTail(DLinkList plist)
{assert(plist != NULL);if(plist == NULL)return;Delete(plist,Listlength(plist));
}
（11）判空
int ListEmpty(DLinkList plist)
{assert(plist != NULL);if(plist == NULL)return -1;if(plist->next == NULL)return -1;return 0;
}
（12）清空链表
void ClearList(DLinkList plist)
{assert(plist != NULL);if(plist == NULL)return;while(!ListEmpty(plist)){DeleteHead(plist);}
}
（13）输出
void Show(DLinkList plist)
{assert(plist != NULL);if(plist == NULL)return;DLinkList p=plist->next;while(p != NULL){printf("%d -->",p->data);p=p->next;}printf("NULL\n");
}